Well, you don’t have ownership over pink hair, so you can be angry, but it’s not going to mean anything. If I got mad every time I saw someone with purple hair I’d be really really angry. Don’t worry about it.
I think you should do what you want and ignore what other people are doing or saying about your life. You never asked for their opinion and their opinions are completely irrelevant. What you do with your hair isn’t up for a public vote. The last I heard, your body was your own.